Answer:
Ava's share = $20
Charlotte's share = $16
Explanation:
15x + 12x = 36 : multiply each girl's age by same amount and adding gives $36
27x = 36 : add x terms
x = 36 / 27 : divide both sides of equation by 27
x = 4 / 3
Ava's share = 15x = 15 * 4/3 = 20
Charlotte's share = 12x = 12 * 4/3 = 16